The basic principle of the stenter frame type «THS» is to have a laboratory machine which has exactly the same possibilities and characteristics as a production machine with the exception of the smaller material width. In developing this unit, major consideration was given to the following points: Spreading devices Optical sensing devices for the control of the corresponding pinning up units Automatic pinning up devices by means of brushes Adjusting possibilities of overfeed and postfeed 2 endless pin chains with corresponding guidings for entry and exit